Electrolytic apparatus for decolorizing food

ABSTRACT

AN APPARATUS FOR DECOLORIZING MELANOIDINS FORMED IN A LIQUID FOOD, UTILIZING AN ELECTROLYTIC CELL WHEREIN THE LIQUID FOOD IS SUBJECTED TO AN ELECTROLYTIC TREATMENT IN AN ELECTROLYTIC CELL HAVING AN ANODE CHAMBER WITH AN ANOLYTIC SOLUTION THEREIN PREFERABLY ISOLATED SO AS NOT TO BE IN DIRECT CONTACT WITH THE LIQID FOOD, A CATHODE CHAMBER HAVING AT LEAST ONE CATHODE MEANS, SAID CATHODE CHAMBER CONTAINING THE LIQUID FOOD, AND ELECTRICAL MEANS FOR SAID ANODE AND CATHODE CONNECTED TO AN ELECTRIC SOURCE. WHERE A PLURALITY OF CATHODE MEMBERS ARE PLACED IN THE CATHODE CHAMBER, EACH CATHODE MEMBER IS PROVIDED WITH RESISTOR MEANS TO MAKE THE CURRENT DENSITY OF THE CATHODES UNIFORM.

April 1974' AKIRA OKUHARA ETAL 3,801,488

ELECTROLYTIC APPARATUS FOR DECOLORIZING FOOD Original Filed March 5),1970 2 Sheets-Sheet 1 F/G. 2 69 n April ,1974 AKIRA OKUHARA ETA-L3,801,488

ELECTROLYTIC APPARATUS FOR DECOLORIZING FOOD Original Filed March 2,1970 I V 2 Sheets-Sheet 2 3,801,488 ELECTROLYTIC APPARATUS FOR IDECOLORIZING FOOD Akira Okuhara and Takashi Nakajima, Noda, and NobuoSaito, Nagareyama, Japan, assignors to Kikkoman Shoya Co., Ltd.,Noda-shi, Japan Original application Mar. 9, 1970, Ser. No. 17,632, nowPatent No. 3,709,802. Divided and this application Aug. 18, 1972, Ser.No. 281,760

Int. Cl. B01k 3/10 US. Cl. 204-252 6 Claims ABSTRACT OF THE DISCLOSUREAn apparatus for decolorizing melanoidins formed in a liquid food,utilizing an electrolytic cell wherein the liquid food is subjected toan electrolytic treatment in an electrolytic cell having an anodechamber with an anolytic solution therein preferably isolated so as notto be in direct contact with the liquid food, a cathode chamber havingat least one cathode means, said cathode chamber containing the liquidfood, and electrical means for said anode and cathode connected to anelectric source. Where a plurality of cathode members are placed in thecathode chamber, each cathode member is provided with resistor means tomake the current density of the cathodes uniform.

This is a division of application Ser. No. 17,632, filed Mar. 9, 1970,now Pat. No. 3,709,802.

This invention relates to a method for improving a quality of a food andfurther maintaining the quality of the food, and more particularly to amethod for decolorizing melanoidins formed during the storage of aliquid food and controlling formation of the melanoidins.

The term liquid food herein used means not only foods consisting only ofliquids, for example, soy sauce, sauce, amino acid solution, Mirin,etc., but also foods consisting of liquids and solids, for example,fruit juice, certain kinds of sauces, etc.

The term mirin herein used means a sweet kind of sake prepared by addingglutinuous rice to distilled alcohol obtained from starch as a rawmaterial and digesting the resulting admixture with the mold riceprepared by culturing the microorganism Aspergillus on steamed r1ce.

The term decolorizing herein used means not only decolorization ofmelanoidins already formed, but also control of formation of themelanoidins and maintenance of the liquid food at the desired degree ofcolor.

When a liquid food is preserved, particularly when the liquid food ispreserved in a storing facility such as a storing tank for a long periodof time, deteriorations in appearance and tastes due to color change offood ingredients and quality change of food ingredients by oxidation area great problem.

Heretofore, anti-oxidants and color change inhibitors have been used toprevent such deteriorations. However, there are few antioxidants thathave a satisfactory effect upon the deteriorations. Even if they have asatisfactory effect, they have an undesirable taste or a toxicity, orhave a good effect at the beginning but have an adverse effect after asubstantially long period of time. Thus, satisfactory antioxidants havenot been available.

As regards the color change inhibitor, particularly, inhibitors forpreventing the browning reaction without an oxidation only sulfurousacid and cystein have been known. It is well known that the action ofthese inhibitors to prevent the browning reaction to brown is due toformation of a chemically stable compound by combination of theinhibitor with such carbonyl compounds as sugars, etc. However, theseinhibitors give also an undesirable United States Patent Patented Apr.2, 1974 influence to the taste. Moreover, sulfurous acid is so toxicthat its use is not preferable.

Therefore, the decolorization of melanoidins formed during thepreparation or storage is limited to an adsorption decolorization methodbased on the use of activated carbon, Japanese acid clay, decolorizingresin or other adsorbents, and any other methods have not been usedalmost at all. However, these adsorbents are liable to adsorb the tasteitself of the food other than the melanoidins, or a larger amount of theadsorbent is necessary to use, or separation of the adsorbent isdiflicult to effect after the adsorbing operation, or regeneratingoperation is necessary for repeated use of these adsorbents. Thus, theuse of the adsorbents has such disadvantages as much labor and expenses.

Furthermore, the adsorbents are not applicable to a liquid foodcontaining solids at all, and thus the oxidation of the liquid foodcannot be prevented at all.

It is an object of the present invention to provide a method forpreventing formation of malenoidins during the preparation and storageof a liquid food.

A further object of the present invention is to provide a method fordecolorizing melanoidins formed in a liquid food by reduction.

In order to accomplish said objects, the present inventors have madevarious researches and studies, and have found that a color of a liquidfood, for example, a coloring matter consisting mainly of the so-calledmelanoidins, which is presumed to form owing to the amino-carbonylreactions, as a factor for changing a color of soy sauce, amino acidsolution, Mirin, fruit juice, etc., can be readily eliminated byapplying an electrolytic reduction to the liquid food.

Furthermore, the present inventors have found that it is possible topreserve a liquid food for a long period of time without forming anymelanoidins by slowly carrying out the reduction over a prolonged periodof time.

According to the present invention, the decolorization can be attainedeconomically at a low cost without any fear of deteriorating the foodtaste or toxicity. The present method can be carried out by placing ananode and a cathode in contact with a liquid food to be decolorized andapplying an electrical potential to the electrodes through the liquidfood. The anode may be used in a direct contact with the liquid food,but it is preferable to provide an anode chamber for isolating the anodefrom the liquid food by means of an ion-permeable material, for example,an agar bridge containing ions, asbestos sheet, ion exchange membrane,etc. as an isolating membrane. -In the anode chamber, an aqueoussolution of such an electrolyte as potassium chloride, sodium chloride,citric acid, tartaric acid or acetic acid is placed together with theanode.

Generally, it is well known that the discharge voltage of hydrogen iondepends upon the respective kind of a cathode. Such metals as aluminum,silver, iron and copper have higher discharge voltages of hydrogen ionand can satisfactorily decolorize the melanoidins of such liquid foodsas soy sauce. In the case of a concentrated solution of a liquid food,for example, soy sauce, the voltage is in an almost linear relation withthe current, and by increasing the cathode current, the decolorizationcan be rapidly effected, while discharging the hydrogen. These metalsare used as a cathode in the present invention. On the other hand, ahardly-ionizable material, for example, platinum or carbon is used as ananode on account of its less consumption.

In the case that carbon or platinum is used as the anode, anelectromotive force ranging from 1.5 to 2.0 v. develops when such areadily-ionizable metal as aluminum, iron or copper is used as thecathode, and the cathode of the electrolytical cell is liable to undergocorrosion if the applied electric potential is less than saidelectromotive force, and electrons are released from the cathodematerial and pass to the anode through the electrolytic cell and thecircuit outside the electrolytic cell. Therefore, when the reduction iscarried out desirably under a low potential less than the electromotiveforce, it is advantageous to use the similar, readily-ionizable metal,for example, the same metal as that of the cathode, as the anodematerial. The decolorization by reduction under a low voltage iseconomical in view of the quantity of electricity (volt ampere) It isdesirable from an economical point of view that the applied potential beas low as possible, but the applied potential depends upon an electricalresistance of a liquid food to be decolorized, particularly upon aresistance due to the ion permeability of the isolating membrane, butgenerally ranges from about one volt to several tens volts. That is tosay, in the case that there is a considerably high resistance betweenthese two electrodes, no current passes between the electrodes unless apotential of several tens volt or higher is applied therebetween, andthe rate of decolorization is made low. Particularly, in the case thatcontamination of the liquid food with cations is undesirable, it isnecessary to make as small as possible the area of the ion-permeable,isolating membrane interposed between the anode chamber and the cathodechamber. In such a case, a current flow is decreased under a lowvoltage, and thus the electrolytic reduction must be carried out, whileapplying a considerably high potential between the cathode and theanode.

The desirable decolorization can be usually attained by passing thecurrent between the two electrodes for a few to several tens hours, butdepends upon the kind of a liquid food and the amount of melanoidinscontained in the liquid food.

In the case that a liquid food is preserved for a long period of timeand its quality is kept constant from the deterioration, it is possibleto pass a current intermittently or continuously between the anode andthe cathode. The decolorization can be efiiciently carried out bystirring or allowing the liquid food to move Within the cell.

When a chloride is used as an electrolyte for an anolyte, a chlorine gasis generated. The generated chlorine gas may be discharged to atmosphereas such, but can be readily reduced to hydrogen chloride by placing itin contact with an activated carbon at the normal temperature or above.Therefore, the chlorine gas can be readily removed from the system byconducting the electrolysis while reducing it with the activated carbon.

The pH of a liquid food within the cathode chamber is graduallyincreased during the electrolytic reduction. When a slight increase inpH is undesirable, the pH can be adjusted by adding a suitable acid tothe liquid food, when desired. For example, in the case of soy sauce,chlorine ions and hydrogen ions are consumed at the anode and thecathode respectively, and thus the pH is adjusted by adding hydrochloricacid thereto.

Preferable embodiment of the present invention is that the electrolyticreduction is carried out by using a double or multiple cathode providedby inserting at least one metallic net or perforated plate cathodebetween the anode and the cathode. In order to carry out an effectivereduction, a larger surface area of a cathode per current is desirable,but an attempt to increase the surface area, for example, by spirallywinding a metal plate cathode around the anode is not effective, becausean even current density cannot be obtained. However, it is found that areduction efliciency can be increased by disposing a metallic net orperforated plate as a double or multiple cathode to increase the surfacearea of the cathode. Furthermore, the use of metallic net cathodes isparticularly effective for electrolytic reduction of a liquid food witha high viscosity or in a slurry state or a liquid food not suitable forstirring.

Such a metallic net or perforated plate cathode is used also tofacilitate the dispersion of the liquid food at the cathode surface andmake uniform a distribution of current density at the cathode surface.In the case of a largescale cell, it is impossible to keep uniform thedistribution of current density at the cathode surface only by the useof the metallic net or perforated plate cathode. In such a case, theuneven distribution of the current density due to a locational relationbetween the anode and the cathode, as well as a locational relationbetween the cathodes themselves can be made by adjusting the voltagesapplied to the individual cathodes and consequently making uniform thecurrent per unit area. In this manner, the reduction efliciency can beincreased. In that case, the volt-.

ages applied to the respective cathodes are adjusted by means of atleast one resistor attached to each cathode.

The use of metallic net or perforated plate cathodes ensures an increasein the surface area of the cathodes and keep the current densityelfectively uniform, whereby the decolorization or electrolyticreduction of the melanoidins can be efficiently carried out.

When a plurality of metallic net or perforated plate cathodes aredisposed against one anode, a plurality of cylindrical cathodes havingdifferent diameters can be arranged coaxially around a center of theanode or a plurality of fiat cathodes can be arranged vertically atproper distances against the anode. Furthermore, when a longitudinallyextended electrolytic cell is employed, a plurality of flat cathodes canbe arranged horizontally at proper distances against the anode.

Now, typical cells used in the present invention will be explained,referring to the accompanying drawings:

FIG. 1 is a schematic cross-sectional side view of an electrolytic cellwherein an anode is in direct contact with a liquid food to bedecolorized.

FIG. 2 is a schematic cross-sectional view of an electrolytic cellwherein an anode is isolated from a liquid food by means of a partitionwall.

FIG. 3a is a schematic plane view ofan electrolytic cell using an anodeisolated from a liquid food by a partition wall and a double cathode,and FIG. 3b is a schematic crosssectional side view of the electrolyticcell shown in FIG. 3a.

FIG. 4 is a schematic cross-sectional side view of one embodiment of anelectrolytic cell employed with reference to Example 15, which follows.

In FIG. 1, numeral 11 is three cathodes consisting of metallic nets orperforated plates and surrounding an anode 12 consisting of carbon. Thecathodes 11 and the anode 12 are placed in a vessel 13. The plus andminus symbols represent the positivity and negativity of the electrodes,respectively. A liquid food is placed in the vessel 13. A currentdensity can be made uniform by providing a resistor between threecathodes, though the resistor is not shown in the drawing.

In FIG. 2, cathodes 21 having the same structure as in FIG. 1 surroundan anode 22, which is isolated from a liquid food by an isolatingmembrane 25 consisting of a ceramic tube, and a stopper 26, whereby ananode chamber 23 is formed. The anode 22, the anode chamber 23 and thecathodes 21 are placed in a vessel 24, in which the liquid food isplaced. The electrolyte solution is placed in the anode chamber 23. Theplus and minus symbols represent the positivity and negativity of theelectrodes, respectively. A current density can be made uniform byproviding a resistor between the cathodes.

In FIGS. 3a and 3b, a double cathode consists of a cylindrical metallicnet or perforated plate 31 and a cylindrical metal plate 32 positionedoutside the cylindrical net or perforated plate 31 coaxially at an anode33. The anode 33 is isolated from a liquid food by an isolating membraneconsisting of a ceramic tube 36 and a stopper 37 to form an anodechamber 34. The anode 33, the anode chamber 34 and the double cathodeare placed in a vessel 35, in which the liquid food is placed. Anelectrolyte solution is placed in the anode chamber 34. The symbol Erepresents a direct current electric source.

In FIG. 4, a carbon rod anode 46 is isolated from raw soy souce 47filled in a polyvinyl chloride cylindrical container 41 having adimension of 200 mm. x 1200 mm. height by an ion-permeable anode chamberconsisting a polyvinyl chloride cylinder having a diameter of 20 mm. 0and an ion-permeable ceramic disc stopper having a diameter of 25 mm. atthe bottom of the cylinder. An aluminum net, ring form cathode 42 havinga size of 190 mm. and 15 mm. height and another aluminum net, ring formcathode 43 having a size of 190 mm. and 75 mm. height are placed in thecontainer 41.

Raw soy sauce 47 and a saturated NaCl solution 48 are placed in thecontainer 41 and the anode chamber, respectively. The plus and minussymbols represent the positivity and negativity of the electrodes,respectively.

Now, the present invention will be explained, referring to examples, butshould not be construed as limitative to these examples.

In examples, the color intensity is determined as follows:

For the soy sauce and amino acid solutions, a ten-fold diluted solutionis prepared and an absorbancy of a mm. solution layer is measured with alight having a wavelength of 500 me.

For the concentrated apple juice and Mirin, the absorbancy of a lO-mm.solution layer without any dilution is measured with a light having awavelength of 500 mp.

A saturated NaCl solution is used as an anolyte when raw soy sauce,amino acid solution and Mirin are used, unless otherwise specified.

EXAMPLE 1 A 42 mm. x 225 mm. silver net [mesh size (center-tocenter):0.6 mm.] was used as a cathode, a carbonrod as an anode, a 100-ml. testtube as a cathode chamber, a 50m]. beaker as an anode chamber. Asaturated potassium chloride solution was placed in the anode chamber,and the cathode chamber and the anode chamber were connected to eachother with a potassium chloridesaturated agar bridge, whereby anelectrolytic cell was formed. In the electrolytic cell, 100 ml. of rawsoy sauce was placed and a direct current was passed between these twoelectrodes under a potential of 3.3 v., and the liquid temperature waskept at 50 C. Reduction was continued for about 6 hours with a currentof 22 ma., whereby the decolorization was efiected as shown below:

Absorbancy before the reduction 0.419 Absorbancy after the reduction0.361

EXAMPLE 2 Electrolytic reduction was conducted at the normal temperaturefor 16 hours under a potential of 3.3 v. with a current of 18 ma., usingthe same cell and soy sauce as in Example 1.

The absorbancy of the reduced soy sauce was formed to be 0.329, and thedecolorization was satisfactorily effected, as compared with theabsorbancy before the reduction of 0.419.

EXAMPLE 3 Raw soy sauce was decolorized, using the same electrolyticcell as in Example 1, except that a copper plate having an entiresurface area of 200 cm. was used as a cathode. The potential and thecurrent were 1.7 v. and 4 ma., respectively. The reduction was conductedat the normal temperature for 7 hours.

Absorbancy before the reduction 0.426 Absorbancy after the reduction0.374

EXAMPLE 4 A spirally-wound aluminum plate having an entire surface areaof 0.27 m? was used as a cathode, a carbon rod as an anode, a 3 l.beaker as a cathode chamber and an isolating membrane of ceramic tube asan anode chamber, whereby an electrolytic cell as shown in FIG. 2 wasformed. In the cell, 3 l. of raw soy sauce was placed and subjected toreduction at the normal temperature under a potential of 3 v. with acurrent of 5.3 ma. for 43 hours.

Absorbancy before the reduction 0.433 Absorbancy after the reduction0.325

EXAMPLE 5 An iron plate having an entire surface area of 475 chloridehaving an ion-permeable ceramic disc as an anode -ml. beaker as acathode chamber, and a polyvinyl chloride having an ion-permeableceramic disc as an anode chamber, whereby an electrolytic cell, wasformed. In the cell, about 100 ml. of raw soy sauce was placed andsubjected to reduction at 27 C. under a potential of 5 v. with a currentof 19 ma. for 4 hours.

Absorbancy before the reduction 0.440 Absorbancy after the reduction0.361

The decolorization was satisfactorily effected.

EXAMPLE 6 100 ml. each of pasteurized soy sauce and an amino acidsolution (prepared by hydrolyzing defatted soy bean with hydrochloricacid) were subjected to reduction, in dependently, at 50 C. under apotential of 4 v. with a current of 2.5 ma. for 6 hours, using the sameelectrolytic cell as in Example 5, except that an aluminum plate havingan entire surface area of 475 cm. was used as a cathode.

Before After reduction reduction Pasteurized soy sauce 0. 834 0. 598

Amino acid solution 0. 312 0. 233

EXAMPLE 7 About 100 ml. of concentrated apple juice was subjected toreduction at the normal temperature under a potental of 3 v. with acurrent of 1.2 ma. for 38 hours, using the same apparatus as in Example5, except that an aluminum plate having an entire surface area of 240cm. was used as a cathode and an aqueous saturated citric acid solutionwas used as an anolyte solution.

Absorbancy before the reduction 0.694 Absorbancy after the reduction0.234

EXAMPLE 8 100 ml. of colored Shiro-Mirin bottled and stored in a housefor about three years was subjected to electrolytic reduction at theordinary temperature under a potential of 3.3 v. with a current of 0.4ma. for about 16 hours, using the same cell as in Example 7, except thatan aqueous saturated sodium chloride solution was used as an anolytesolution.

Aborbancy before the reduction 0.199 Absorbancy after the reduction0.123

Decolorization was considerably effected.

EXAMPLE 9 llOrna. (value obtained one hour after the start of currentpassage) for about 20 hours, while gently stirring the soy sauce bymeans of a magnetic stirrer.

Absorbancy before the reduction 0.419 Absorbancy after the reduction0.238

7 EXAMPLE 10 Absorbancy before the reduction 0.454 Absorbancy after thereduction 0.324

EXAMPLE 11 In an electrolytic cell consisting of a cathode chamber of55-ml. test tube, an aluminum plate anode having-a size of 20 mm x 300mm., a multiplily folded aluminum foil cathode having an entire surfacearea of 200 cm. and an anode chamber of KCl-saturated agar bridge, 50ml. each of raw soy sauce was placed and subjected to reduc tion. Thecurrent and absorbancy of the decolorized soy sauce were measured, whilevarying the voltages applied between the two electrodes. The result isgiven in the following table. The current was passed for 15 hoursat theordinary temperature. The absorbancy before the reduction was 0.451.

Current Absorb- (ma ancy EXAMPLE 12 In an electrolytic cell as shown inFIG. 1 and consisting of a cathode chamber of 2-l. beaker, an aluminumnet cathode having a size of 170 mm. X 380 mm. [mesh size(center-to-center): 4 mm.], and a carbon rod anode, 2 l. of raw soysauce was placed and subjected to reduction at room temperature under apotential of 2.5 v. with a current of 100 ma./l. for 16 hours, whilegently stirring the soy sauce with a magnetic stirrer.

Absorbancy before the reduction 0.367 Absorbancy after the reduction0.244

EXAMPLE 13 2 l. of concentrated fresh apple juice was subjected toreduction at room temperature under a potential of about 4 v. with acurrent of 25 ma./l. for 16 hours, using the same cell as in Example 12,while gently stirring the juice with a magnetic stirrer.

Absorbancy before the reduction 0.949 Absorbancy after the reduction0.716

EXAMPLE 14 Absorbancy before the reduction 0.372 Absorbancy after thereduction 0.141

The amounts of increased color intensity per hour of the original soysauce and the reduced soy sauce were compared by heating these twosolutions to C., and was found to be 0.08 for the original solution and0.05 for the reduced solution, respectively.

EXAMPLE 15 37 l. of raw soy sauce was subjected to reduction with acurrent of 18 ma. for 74 days, using the cell shown in FIG. 4. Theaverage liquid temperature was 27 C., because the ambient temperaturewas high. The pH of the solution was 5.0 after the electrolysis wascompleted, and was adjusted to 4.80 (the original value) by addingconcentrated HCl thereto.

Absorbancy before the reduction 0.351 Absorbancy after the reduction0.371

The absorbancy of soy sauce preserved for the same days without anyreduction was 0.553.

EXAMPLE 16 In an electrolytic cell as shown in FIGS. 3a and 3b andconsisting of a carbon rod anode, a cathode chamber of 2-1. beaker, aninside aluminum cylindrical net cathode having a size of 160 mm. x 290mm. [mesh size (centerto-center): 4 mm.] an outside aluminum cylindricalnet cathode having a size of 170 mm. x 380 mm. (the same mesh size asthat of the inside net cathode), and an anode chamber of ceramic tubemembrane, 2 l. of raw soy sauce was placed and subjected to reduction atthe normal temperature under a potential of 2.0 v. with a current ofma./l. After the completion of the reduction, the pH of soy sauce wasadjusted to the original pH by adding HCl thereto. Then, the soy saucewas heated to 80 C. for 3 hours, cooled and subjected to a sensoryevaluation test.

Number of panel members is 12 for the taste test and 14 for the flavortest, and total square is 114 for the taste test and 25 for the flavortest, respectively, and it was found that there are no significantdifferences as regards both taste and flavor.

EXAMPLE 17 In an electrolytic cell A as shown in FIGS. 3a and 3b andconsisting of an outside aluminum plate cathode having an entire surfacearea of 0.13 m an inside aluminum net cathode having a size of mm. x 290mm. [mesh size (center-to-center): 4.0 mm], a carbon rod anode, acathode chamber of 2-1. beaker, and an anode chamber of ceramic tube andan electrolytic cell B having the same structure as the cell A exceptthat a spirally-wound aluminum plate having an entire surface area equalto the entire surface area of the outside cathode and the inside cathode(wherein the surface area of the inside cathode is calculated as aplate) was used as a cathode, 2 1. each of soy sauce was placed andsubjected to electrolytic reduction at the normal temperature under apotential of about 2.2 v. with a current of about 45 mc. for

The use of aluminum net cathode was very effective in reductionefiiciency under the same conditions of current and reduction time.

EXAMPLE 18 2 1. each of concentrated apple juice was subjected toreduction at the normal temperature under a potential of 4.5 v. with acurrent of 100 ma. for 17 hours, using the same two cells as in Example17 and a saturated citric acid solution as the anolyate solution.

Absorbancy before the reduction 0.854

Absorbancy after the reduction:

Spirally wound cathode 0.620 Net cathode 0.549

What is claimed is:

1. An apparatus for decolorizing a liquid food, which comprises an anodechamber having an anode therein and a single cathode chamber havingtherein a plurality of cathodes comprising perforated plates or metallicnets, each of which cathodes is provided with at least one resistor formaking the current densities at said cathodes uniform, said anodechamber being isolated from the cathode chamber by an ion-permeablematerial, said anode and the cathodes being electrically connected.

2. An apparatus according to claim 1, wherein the cathode chamber ispositioned between two anode chambers, the cathode and both anodechambers are longitudinal and a plurality of fiat cathodes arepositioned horizontally in the cathode chamber,

3. An apparatus according to claim 1, wherein the ion-permeableisolating means is a ceramic or asbestos.

4. An apparatus according to claim 1, wherein the anode chamber and thecathode chamber are electrolytically connected by an agar bridge.

5. An apparatus according to claim 1 wherein the cathode chamber iscylindrical and the anode chamber is positioned at the center of thecathode chamber which is cylindrical.

6. An apparatus according to claim 5 wherein at least two cylindricalcathodes having difierent diameters are positioned coaxially around theanode chamber.

References Cited UNITED STATES PATENTS 1,189,023 6/1916 Watson 204l37 (R1,181,555 5/1916 Vaygouny 204252 1,371,698 3/1921 Linder 204-2633,062,731 11/1962 Durrum 204- G 2,085,898 7/1937 Cardone 204---252 JOHNH. MACK, Primary Examiner W. I. SOLOMON, Assistant Examiner US. Cl. X.R.

204-260, 263, DIG 7 UNITED STATES PATENT OFFICE 7 CERTIFICATE OFCORRECTION Patent No. 3, 8,01 488 Dated April 2, 197

Inventor(s) Okuhara 813.81.

, It is certified that error appears in the above-identified patent;

and that said Letters Patent are hereby corrected as shown below:

Assignee is Kikkoman Shoyu Co. Ltd. rather than Kikkoman shoya Co. Ltd.

Signed-end sealed this 3rd day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PC4050 10-69)

